Differentiation of the cells of the inner cell mass into the specialized cells required for forming the complex tissues that comprise living organisms has traditionally been viewed as a unidirectional process, with cells in the embryo becoming gradually committed to a specific cell type. However, somatic cell nuclear transfer experiments have demonstrated that the oocyte can return the nucleus of an adult differentiated cell into a pluripotent embryonic-like state. While little is known about the factors that induce this process, several recent reports have described the ability of four transcription factors whose retroviral overexpression enabled the induction of a pluripotent state in murine fibroblasts. Simultaneous overexpression of the pluripotency-associated POU domain class 5 transcription factor 1 (Oct3/4), SRY-box containing gene 2 (Sox2), proto-oncogene myc (c-Myc), and Kruppel-like factor 4 (Klf4) led to the generation of induced pluripotent stem (iPS) cells that exhibited morphology and growth properties similar to embryonic stem (ES) cells that were competent for formation of germline chimera. Rrecently investigators have created iPS cells from adult human cells using either a combination of factors similar to the mouse system. These human iPS cells had normal karyotypes, expressed telomerase activity, cell surface markers and genes that typify human ES cells, and maintained the developmental potential to differentiate into advanced derivatives of all three primary germ layers. The successful reprogramming of differentiated human somatic cells into a pluripotent state may not only eliminate the need of controversial use of human ES cells in research applications, it also provides a method to potentially generate customized, patient- specific pluripotent cells for regenerative medicine efforts including cardiovascular tissue engineering. However, this does not obviate the need to critically study the differentiation behavior of iPS cells as directed differentiation protocols will be essential for these stem cell-based therapies to become clinical reality. Our preliminary results suggest that murine iPS cells can be differentiated into cells of the cardiovascular and hematopoietic lineage, and that it is possible to isolate a Flk1-positive progenitor cell from differentiating iPS cells that possesses the ability to differentiate into all three cell types of the cardiovascular lineage. Direct reprogramming of somatic cells to generate patient-matched pluripotent stem cells that could serve as unlimited source of autologous material could revolutionize the treatment of heart disease;however, the differentiation and therapeutic capacity of iPS cells is still unknown. This application will build on the progress we have already made and further explore the biology and therapeutic potential of iPS-derived cardiovascular progenitor cells. PUBLIC HEALTH RELEVANCE: Despite medical advances, cardiovascular disease remains a leading cause of mortality and morbidity. Thus, regenerative cardiovascular therapies that restore normal function would have an enormous societal and financial impact. Reprogramming of differentiated human somatic cells into a pluripotent state may not only eliminate the need of controversial use of human ES cells but it would also provide a mechanism to generate customized, patient-specific pluripotent cells for regenerative medicine efforts including cardiovascular tissue engineering.